1. Field of the Invention
The present invention relates to an exposure control device used in a silver salt photographic type color copying apparatus or a color printer for regulating the amount and components of exposure light.
2. Background of the Prior Art
One such exposure control device which is disclosed in, for example, Japanese Patent Publication No. 44-2542 includes two color filter plates and a variable aperture plate both disposed between front and rear lens groups of a lens system. These color filter plates and variable aperture plate are moved in a direction perpendicular to the optical axis of the lens system so as to regulate the amount and color components of light passed therethrough in order to control the color balance and density of a copy. Each color filter plate includes two color filter sections and a transparent section between the two color filter sections. These two color filter sections have two different colors of the three primary colors, namely blue, green and red, or of cyan, magenta and yellow. One of these three colors is used in both color filters.
Color originals from which copies are made are generally classified into two types, namely color printed materials and color photographic materials. Because of different coloring materials used in these color printed and photographic materials, these two types of materials have different spectral distributions for the three primary colors. As a result, copies of these materials tend to have different color densities and/or color balances. In order to make copies having the same color density and color balance from any one of the two color materials, filters are used according to spectral sensitivities of the photosensitive materials used. In addition, it is required to adjust the color temperature of a light source to match the photosensitive material to be used.
The conventional color copying apparatus with color filter plates to be moved in and out of an optical path requires a filter adjusting mechanism which is complicated in construction and, therefore, make the apparatus large.